This invention relates to an apparatus and a method for repairing and/or monitoring the integrity of a repair to a vessel port.
Vessels used in corrosive and hazardous chemical services are often manufactured from exotic metals such as titanium, tantalum, nickel, nickel/copper alloys, nickel/chromium alloys, nickel/molybdenum alloys, etc. These materials, while providing a measure of protection against leakage of the corrosive, hazardous, and/or lethal materials, are not without drawbacks. Vessels manufactured out of exotic materials are frequently more expensive and usually require sophisticated fabrication techniques.
In order to obtain the advantages of increased corrosion resistance and safety which may be found in vessels manufactured out of exotic materials without the disadvantages noted above, lined vessels are used in corrosive and hazardous chemical service. The vessel liners may be in the form of corrosion resistant coatings or paints, exotic metals, rubber (natural or synthetic), graphite, glass, ceramic, fluorocarbon compounds such as Teflon.RTM. or Kynar.RTM. resins, fiberglass reinforced plastics (FRP), and the like. Generally, lined vessels are fabricated from an inexpensive metal or plastic substrate which provides mechanical and structural support for the liner. The substrate is usually not resistant to corrosion but is protected, nonetheless, from corrosion by the vessel liner.
During its life, the lined vessel is frequently subjected to conditions which decrease the useful life of the vessel due to damage to or failure of the vessel liner. Conditions which may decrease the life of the lined vessel include uncontrolled, rapid heating or cooling of the vessels or vessel contents, exposure of the vessel liner to materials for which the vessel is not designed, poor maintenance practices, exposure of the vessel substrate to corrosive materials, and the like. Furthermore, pinholes and cracks may develop in glass, rubber, metal, and plastic liners due to abuse of the liners during vessel maintenance, corrosion, and/or erosion.
A particularly likely area of lined vessel failure occurs in the vessel ports or flanged connections, particularly on the flange face of the port whereon the vessel liner terminates. Damage to the liner on the face of the flange may be due to improper flange alignment, gasket leakage, improper tightening of the flanges, striking the flange face with a foreign object, the presence of a foreign material between the mating flange surfaces, and the like. In order to utilize a vessel having a damaged liner in the port area of a vessel, it is desirable to plug the port in order to inhibit corrosion of the vessel substrate. Once the damaged vessel port is plugged, the vessel can be used until such time as a permanent repair to the liner can be effected.
Until now, methods and apparatus for plugging or sealing off a damaged vessel port have not provided adequate means for detecting the presence of or preventing leakage of corrosive material past the plug to the area of the vessel port which is no longer sufficiently protected by the vessel liner. One means which is used for repairing a damaged glass liner is to cover and seal the damaged area with a Teflon.RTM. plug and tantalum liner with a Teflon.RTM. seal, then to back fill the sealed area with a filler material such as Pfauder.RTM. S-Filler/Boot Filler or Siloxirane.RTM. C2131 putty. The disadvantage of this method and apparatus is that leakage past the repair can occur due to imperfections in the plug, sealing material and vessel liner as well as permeation of a corrosive material through the plug and seal. It is well known that Teflon.RTM. resin is permeable to halogens such as chlorine and bromine. Furthermore, when the operating pressure inside the lined vessel exceeds the pressure downstream of the plug, leakage or permeation through the sealing material is more likely to occur. There is a need therefore for an apparatus and method for repairing a vessel port which not only protects the vessel substrate exposed due to liner failure, but also allows monitoring of the integrity of the repair.